Vol. 17 No. 2 (2022)
Articles

Comparative cytogenetics on Zamenis lineatus and Elaphe quatuorlineata (Serpentes: Colubridae)

Marcello Mezzasalma
Department of Biology, Ecology and Earth Science, University of Calabria, Via P. Bucci 4/B, 87036 Rende
Elvira Brunelli
Department of Biology, Ecology and Earth Science, University of Calabria, Via P. Bucci 4/B, 87036 Rende
Gaetano Odierna
Department of Biology, University of Naples Federico II, Via Cinthia 26, 80126, Naples
Fabio M. Guarino
Department of Biology, University of Naples Federico II, Via Cinthia 26, 80126, Naples
Published November 7, 2022
Keywords
  • Chromosome,
  • evolution,
  • karyotype,
  • NORs,
  • squamates,
  • snakes
  • ...More
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How to Cite
Mezzasalma, M., Brunelli, E., Odierna, G., & Guarino, F. M. (2022). Comparative cytogenetics on Zamenis lineatus and Elaphe quatuorlineata (Serpentes: Colubridae). Acta Herpetologica, 17(2), 197-203. https://doi.org/10.36253/a_h-13467

Abstract

Because of their peculiar genomic and chromosomal characteristics, reptiles are extraordinary model organisms to study karyotype and sex chromosome evolution, but despite the growing interest in their evolutionary cytogenetics, only a small fraction of species have a known karyotype. We performed a comparative cytogenetic analysis on Elaphe quatuorlineata and Zamenis lineatus, using classic and molecular techniques. We provide the karyotype of these two species and an assessment of their chromosomal features. Chromosome analysis was performed with standard karyotyping, C-banding, sequential C-banding + CMA3 + DAPI and Ag-NOR staining. On E. quatuorlineata, we also performed CMA3-methyl green staining and Fluorescence in situ Hybridization mapping NOR loci (NOR-FISH). Elaphe quatuorlineata and Z. lineatus show a very similar karyotype of 2n = 36, with 8 macro- and 10 microchromosome pairs, but differ in the morphology of the pair 8, which resulted submetacentric in the former and metacentric in the latter species. By comparing our data to those available from the literature on congeneric species, we analysed the occurrence of primitive and derivate chromosomal characters and provide cytotaxonomic insights, which further support the species status of Z. lineatus. In both species, the 4th pair was identified as the sex chromosome pair (ZZ/ZW) and NORs were localized on a microchromosome pair. We finally highlight in both genera Elaphe and Zamenis different stages of heterochromatinization of the W chromosome, in agreement with the progressive diversification model of sex chromosome as already shown in different reptile taxa.

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